In the semiconductor processing industry, there is currently a strong trend toward scaling down existing structures and fabricating smaller structures. This process is commonly referred to as microfabrication. One area in which microfabrication has had a significant impact is in the microelectronic area. In particular, the scaling down of microelectronic structures has generally allowed the structures to be less expensive, have higher performance, exhibit reduced power consumption, and contain more components for a given dimension. Although microfabrication has been widely active in the electronics industry, it has also been applied to other applications such as biotechnology, optics, mechanical systems, sensing devices and reactors.
Typically the fabrication of an electronic device requires several deposition and etching steps that often must be aligned with each other with a degree of accuracy approaching or even exceeding the minimum feature size of the device. Currently, electronic devices are fabricated on flat, inflexible, non-deformable substrates such as crystalline Si or glass using photolithography. However, a much more inexpensive means for producing such devices is based on imprint lithography.
Imprint lithography is typically utilized to pattern thin films on a substrate material with high resolution using contact between a master with the features of the structure to be fabricated and the substrate material to be patterned. The thin films patterned can be dielectrics, semiconductors, metals or organic and can be patterned as thin films or individual layers. Imprint lithography is particularly useful in roll-to-roll processing since it has a higher throughput and can handle wider substrates.
In conventional photolithography, optical alignment marks are used to guarantee alignment between successive patterning steps. Although, it is possible to use optical alignment marks in a roll-to-roll process it is not practical for several reasons. First, it adds additional complexity since the fundamental imprint lithography process is not optical. Next, the lack of planarity of the substrate in a roll-to-roll environment causes difficulties in the accuracy with which optical alignments can be made due to depth of field restrictions and other optical aberrations. Finally, the flexible substrates used in roll-to-roll processing may experience dimensional changes due to variations in temperature, humidity, or mechanical stress. These deformations and/or dilations of one patterned layer with respect to the next may make accurate alignments over a large area impossible.
Accordingly, what is needed is a method and system for fabricating a device that overcomes the above referenced problems related to the roll-to-roll fabrication process. The method and system should be simple, inexpensive and capable of being easily adapted to existing technology. The present invention addresses these needs.